Carbonated soft drinks (CSD) bottles are often packaged in bottles constructed of PET. A non-exhaustive list of such beverages includes colas, seltzers, club soda, ginger ale, Tom Collins mix, root beers, lemon-lime flavored sodas, and a variety of other flavored sodas. At pressures near or below atmosphere, the CO2 in these carbonated beverages escapes rapidly from solution. To keep a sufficient amount of CO2 in solution, the soda is bottled under pressure. Keeping the CO2 in solution is relatively important. Without it, the soda becomes flat, and these beverages would lose much of their appeal. Anecdotal evidence suggests that it is the carbonation that makes the beverages appealing. That is, the CO2 present in the beverage provides a pleasing sensation in the palate. Accordingly, there is a need to insure that a sufficient amount of CO2 remains in the beverage so that the consumer realizes full value for the product.
PET is the material of choice for forming bottles for carbonated beverages, due to its low cost, transparency, moldability, and relatively light weight. Also, its high level of impact resistance renders PET containers virtually unbreakable, a desired feature in a packaging material. However, the barrier properties of PET with respect to gases are somewhat suspect, and over time, CO2 will leak through the container. Also, such containers are typically sealed by a cap having a base and a cylindrical skirt extending downward from the base. The cap has threads on the interior of the skirt, which are complimentary to threads on the container located near the container opening.
It is possible for the pressurized CO2 to escape from the container in the neck region as well. Since it is possible that a beverage may sit in storage for an extended period of weeks, even months, between bottling and use by the consumer, a significant loss of CO2 may arise. In one example, the shelf life of a 12 fluid ounce bottle is 8 weeks and 20 fluid ounce bottle is 16 weeks.
Furthermore, once the consumer opens the bottle, the CO2 is rapidly released. In the case of large sized bottles, which hold a volume in excess of a single serving, it is expected that these bottles will be opened, closed after beverage is dispensed, and then opened at a later time to again dispense beverage. Eventually all of the CO2 in the beverage will be released from the beverage rendering the remaining soda fizzless, a wholly insipid and undesirable state. The consumer is then left with two options, neither satisfactory, in which he or she can consume a flat beverage, or dump the remainder down the drain.